The present invention relates to a supply system for a device, such as a writing instrument, drafting or drawing instrument, painting device, printing device, or the like, that operates with the aid of capillary forces and is used to apply liquid, with the system including receptacle means that accommodates the liquid and is closed off relative to the atmosphere, and also including an application instrument, such as a nib or the like, that communicates with the receptacle means via a feed mechanism and serves for the application of the liquid, for which purpose the application element has a discharge means.
With devices of the aforementioned type, precautions must be taken that liquid can flow out of the discharge means of the application element only when discharge is desired, and also only in the desired quantity; liquid must not discharge only as a result of the force of gravity.
Technical approaches to accomplish these requirements are known. For example, with writing instruments the liquid is frequently stored in an entirely capillary manner, with writing being possible due to the fact that the adhesion of the liquid to the surface, and the ultimate strength of the liquid filament, are greater than those of the capillary holding forces of the liquid in the capillary reservoir. However, in so doing the capillary holding forces must be greater than the force of gravity of the stored liquid, which can only be achieved with very high capillarity starting from the premise that in order to achieve a large writing capacity, the entire capacity of the interior hollow space of the writing instrument should be utilized. Unfortunately, the high capillarity of the reservoir represents a great limitation in the selection of writing nibs, since such nibs must have an even greater capillarity than the reservoir in order to ensure a satisfactory operation of the instrument during the writing, drafting, drawing, painting, printing, etc. process.
With the exception of ball points or roller balls, writing nibs having a high capillarity are for various reasons at the present time not suitable for longer writing periods due to an inadequate wear resistance.
A further drawback of the aforementioned type of known reservoir or storage system is that due to a nonuniform construction resulting from manufacture, the reservoir cannot discharge or dispense the entire quantity of writing fluid, with the disadvantageous result that the stroke intensity diminishes during a continued emptying of the reservoir.
Pursuant to another known approach for holding liquid above a discharge opening of an application element without automatic dispensing, the liquid that is to be applied is held in a closed receptacle via a partial vacuum and the capillarity of an air inlet opening. The capillarity of the air inlet opening must be such that at least the liquid column can be held that extends from the air inlet opening to the opening of the application element. In practice, with this arrangement considerably smaller capillarities can be realized than with the previously described capillary storage system. Accordingly, the capillarity of the writing nib could also be lower than is required, for example, for fountain pens and ink drawing instruments.
A drawback of this type of liquid storage is that as emptying of the receptacle increases, the air that replaces the liquid expands as the air pressure decreases and/or the temperature increases, so that part of the liquid escapes from the receptacle. To prevent liquid from dripping from the device, the liquid that escapes from the receptacle is collected in capillary reservoirs that are expressly provided for that purpose. If subsequent thereto the temperature again drops, the liquid must be drawn back into the closed receptacle from the capillary reservoir in as complete a manner as possible, since otherwise the capillary reservoir would overflow after a number of temperature fluctuations. The reliability of this system decreases as the volume of the receptacle increases.
It is an object of the present invention to provide a supply system of the aforementioned general type that on the one hand is in a position to accommodate very large writing fluid volumes, and that on the other hand is practically independent of the temperature and air pressure fluctuations that can be expected during normal operation, with such a supply system permitting writing instruments, drafting or drawing instruments, painting devices, printing devices, etc. to be produced with wear resistant material only at the writing nib or the like, hence making it possible to produce the devices as a whole in an economical manner. It is a further object of the present invention to provide a supply system that makes it possible to completely empty the writing fluid from the receptacle provided therefor, and that prevents writing fluid from dripping out of the device that is equipped with such a supply system.